feat: added a specific message depending on failure type

[kevkevinpal]

summary

This is just an idea of what we can do (setting as draft for now to get wording correct)

Closes #388

---

Example message

[kevkevinpal]

When testing on an expired invoice I get a parsing error.

What would make more sense to me is to show the user that the invoice is expired instead of either not showing anything in the UI or saying parsing error when scanned

[m1sterc001guy]

Screenshot looks great. This is definitely an issue in the app right now. I'm not sure thrilled about string matching to determine the error though, as that is kind of brittle. But right now that's all we can probably do since I don't know if we have any better way of propagating errors from rust -> flutter.

Would you be interested in researching how to propagate errors properly from rust -> flutter? I suspect there's a lot more places in the code that would benefit from this